I've universally heard them referred to as hard rock.
I honestly don't care too much whether he goes on the list or not (even though he is a fantastic guitarist) but here you go.
Coupling the technical proficiency of Bettencourt's guitar with a funky rhythmic base, the band issued a self-titled debut album in 1989. It peaked at number 80 -- a modest showing for a new, unseasoned band -- and the song "Play with Me" was used to orchestrate the chase scene during Bill & Ted's Excellent Adventure. Extreme had begun to earn respect in the heavy metal world, but it wasn't until the arrival of the band's follow-up effort, Pornograffitti (particularly the the Everly Brothers-style acoustic ballad "More Than Words"), that a mainstream audience latched onto the group's sound... (AMG)http://rateyourmusic.com/artist/extremehttp://en.wikipedia.org/wiki/Extreme_%28band%29
EDIT - However, they aren't listed as metal on metal-archives, which is the site I use for questionable hard rockbands, so my vote is to keep him off just to be consistent.